This invention relates to an infrared and ultraviolet radiation absorbing glass. The glass has a neutral gray color and sufficiently high transmittance for visible light and is particularly suitable for use in building and vehicle windows.
For windows of buildings, automobiles and other vehicles there is an increasing demand for sheet glass that is sufficiently transparent to visible light and absorptive of not only infrared rays but also ultraviolet rays.
It is known to render a soda-lime-silica glass absorptive of infrared and ultraviolet rays by incorporating iron in the glass. Ferrous iron expressed as FeO provides the glass with the absorption of infrared radiation, whereas ferric iron expressed as Fe.sub.2 O.sub.3 provides the glass with the absorption of ultraviolet radiation. In practice Fe.sub.2 O.sub.3 is used as the source of the entire iron, and an adequate portion of Fe.sub.2 O.sub.3 is reduced to FeO during the glassmaking process.
Also it is known to incorporate CeO.sub.2 and/or TiO.sub.2 in a soda-lime-silica glass for the absorption of ultraviolet radiation.
From an industrial point of view, it is desired that an infrared and ultraviolet absorbing glass in the form of sheet glass can be produced without significantly changing the conditions of conventional glass melting and refining operations. Also it is desired that an infrared and ultraviolet absorbing glass sheet can easily be toughened by a conventional tempering method. Besides, an infrared and ultraviolet absorbing glass sheet is desired to have a pleasing tint such as neutral grayish tint.
JP-A-3-153543 shows a neutral gray colored infrared and ultraviolet absorbing glass containing as fundamental components, on a weight basis, 68-75% of SiO.sub.2, 10-18% of Na.sub.2 O, 5-15% of CaO, 0-5% of MgO, 0-5% of Al.sub.2 O.sub.3 and 0-5% of K.sub.2 O, if necessary, small amounts of a melting agent and a clarifying agent, and a coloring agent consisting essentially of 0.4-0.7% of Fe.sub.2 O.sub.3 (total iron), 0.08-0.15% of FeO, 0.003-0.008% of Se, 0.003-0.025% of CoO and 0.022-0.050% of Cr.sub.2 O.sub.3. This glass exhibits at a thickness of 5.56 mm that visible light transmittance is less than 20%.
JP-A-2-64038 shows a glass composition which is dark and neutral gray in color and nickel-free. This glass contains as base glass composition, on a weight basis, 68-75% of SiO.sub.2, 10-18% of Na.sub.2 O, 5-15% of CaO, 0-5% of MgO, 0-5% of Al.sub.2 O.sub.3 and 0-5% of K.sub.2 O, traces of melting and refining aids, if any, and colorants consisting essentially of 0.55-1.0 wt % of Fe.sub.2 O.sub.3, 0.003-0.02 wt % of Se and 0.005-0.02 wt % of CoO, wherein at least 15% of the iron is in the ferrous state. This glass has a luminous transmittance of no more than 20% at a thickness of 5.56 mm. The portion of the iron in the ferrous state constitutes 0.09-0.3 wt % of the total glass composition. However, the above-mentioned glasses which are disclosed in JP-A-3-153543 and JP-A-2-64038 exhibit at a thickness of 5.56 mm that visible light transmittance is less than 20%. Therefore, it is difficult to use these glasses for automotive windows.
JP-B-56-41579 discloses a gray-colored infrared absorbing glass which contains, as fundamental components, on a weight basis, 70-75% of SiO.sub.2, 1-2% of Al.sub.2 O.sub.3, 5-10% of CaO, 1-5% of MgO and 10-15% of R.sub.2 O (total of Na.sub.2 O and K.sub.2 O), with a proviso that the molar ratio of K.sub.2 O to R.sub.2 O is from 1/4 to 3/4, and as coloring agents, on a weight basis, 0.1-0.2% of Fe203, 0.02-0.06% of NiO, 0.001-0.004% of CoO and 0.01-0.5 MnO. This glass has a blue-purple or red-purple color. This glass uses NiO as a coloring agent. Therefore, the glass may change in color or be fractured upon heating. The molar ratio of K.sub.2 O to R.sub.2 O of this glass may not satisfactory to be used for automotive windows.
JP-B-55-23221 discloses an infrared absorbing glass which contains, as fundamental components, on a weight basis, 65-75% of SiO.sub.2, 0-5% of Al.sub.2 O.sub.3, 5-15% of CaO, 0-10% of MgO, 10-18% of Na.sub.2 O and 0-5% of K.sub.2 O with provisos that the total of CaO and MgO is 6-16% and the total of Na.sub.2 O and K.sub.2 O is 10-20%, and as coloring components 0.05-1.0% of Fe.sub.2 O.sub.3, 0.05-5.0% of MnO.sub.2, 0.002-0.1% of CR.sub.2 O.sub.3 and 0.005-0.3% of CuO. This glass having a neutral gray or bronze color exhibits at a thickness of 5 mm that visible light transmittance is in a range from 35 to 65%. This is unsatisfactory to be used for automotive windows.
JP-B-52-49010 discloses a neutral gray-colored glass which contains, as fundamental components, on a weight basis, 68-75% of SiO.sub.2, 0-5% of Al.sub.2 O.sub.3, 5-15% of CaO, 0-10% of MgO, 10-18% of Na.sub.2 O and 0-5% K.sub.2 O with provisos that the total of CaO and MgO is 6-15% and the total of Na.sub.2 O and K.sub.2 O is 10-20%, and as coloring components 0.1-0.5% of Fe.sub.2 O.sub.3, 0.003-0.02% of CoO, 0.0005-0.001% of Se and 0-0.002% of NiO. This glass exhibits at a thickness of 5 mm that visible light transmittance is from 57 to 63%, that solar radiation transmittance is from 57 to 63%, and that transmitted light color purity is not greater than 1.5%. This glass is insufficient in visible light transmittance and ultraviolet absorption.